862 H. H. NEWMAN AND J. THOMAS PATTERSON 
tion and heredity in but one of these shields, it is not necessary 
to enter upon a description of the elements of the others, except 
in so far as such an account would be of help in understanding 
the character of the elements in the particular region in question. 
The nine bands are united to one another by strips of flexible 
skin which permit considerable motion in this part of the armor. 
The first band is attached in a similar manner to the scapular 
shield, while the integument joining the ninth band to the pelvic 
shield may be present only toward the ends of the band, in which 
case the middle of the band is firmly united to the shield. The 
soft parts of the body lying directly beneath the strips of flexible 
skin are not exposed, because of the fact that the bands overlap 
one another for a distance equal to about one-third their width, 
that is, the posterior margin of any band overlaps the anterior 
third of the succeeding band. On account of this overlapping 
the banded region as a whole presents a distinctly testudinate 
appearance. ; 
Each band is composed of a number of elements, of which there 
are three kinds: (1) the thick, bony, dermal plates covering the 
under surface of the band and constituting its main body; (2) the 
thin, horny, epidermal scutes which cover the posterior exposed 
part of the band; and (3) the associated hair group. 
Each bony plate is oblong in outline, with its long axis consti- 
tuting the width of the band, and in the adult animal has an 
average width and length of 6 mm. and 30 mm., respectively. 
As we shall see later, the number of these plates varies in differ- 
ent bands as does also the number for the same band in different 
individuals, but in round numbers there are on the average about 
62 plates to the band. 
The epidermal scutes, unlike the underlying bony plates, are 
of two types, which we may call primary and secondary. The 
first of these is represented by a wedge-shaped area having a 
slightly convex upper surface, and with its base forming a part 
of the posterior margin of the band (fig. 20). The base of each 
scute has two notches which are situated so as to divide the margin 
into three areas of about equal width. In reality the notches are 
but the mouths of hair pits located in the underlying bony plate 
